Sm3+/Pr3+ biactivated Ca3Y2Ge3O12:0.04Sm3+:Pr3+ red phosphor with high thermal stability for low correlated temperature WLED

Highlights: • Pr³⁺ can improve PL properties of Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺:0.003Pr³⁺. • Phosphor Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺:0.003Pr³⁺ exhibited a splendid thermal stability. • Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺:0.003Pr³⁺ based WLED exhibited a low CCT and a high R_a. Sm³⁺ and Pr³⁺ ion co-doped phosphors Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺:yPr³⁺ (0.001 ≤ y ≤ 0.006 mol%) were synthesized by high tempereture calcination process. The XRD results showed that samples Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺:yPr³⁺ (0.001 ≤ y ≤ 0.006) were matched well with the standard profile Ca₃Y₂Ge₃O₁₂ (PCSD No. 27–0092) which possessed a cubic structure with the space group Ia-3d (230), and these synthesized samples exhibited irregular particles with large size of about 40 μm. The photoluminescence (PL) study demonstrated that the co-doped Pr³⁺ ions could improve the PL properties through the energy transition (ET) process between Pr³⁺ ions and Sm³⁺ ions, leading to a smaller liftimes of Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺:0.003Pr³⁺ than Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺. The optimum Pr³⁺ ions doping concentration was y = 0.003 and the CIE coordinates (0.5249, 0.4730) of Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺:0.003Pr³⁺ lied in red light region. Notably, sample Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺:0.003Pr³⁺ exhibited better thermal stability and larger activation energy (E_a) by compariton of Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺. Finally, the WLED device based on Ca₃Y₂Ge₃O₁₂:0.04Sm³⁺:0.003Pr³⁺, (Ba, Sr)₂SiO₄: Eu²⁺ and an ultraviolet chip of 395 nm exhibited a low correlated temperature (CCT) of 3929 K and a color rendering index (R_a) of 89.